// all的用法
let p1 = new Promise((resolve) => {
    resolve('这里是p1')
})
let p2 = new Promise((resolve) => {
    resolve('这里是p2')
})

Promise.all([p1, p2]).then(([p1Res, p2Res]) => {
    console.log('all', p1Res, p2Res)
})